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RAVENNA GRASS A NOXIOUS WEED ESCAPEE FROM GARDENS

GARDEN TIPS – written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written August 6, 2015

RAVENNA GRASS A NOXIOUS WEED ESCAPEE FROM GARDENS

Most gardeners I know are concerned about the environment and would be upset to learn that about half noxious weeds in this country were introduced by gardeners like themselves. Gardeners are always excited to find an interesting or unique new plant for their yards and gardens. Unfortunately, some of these plants escape the confines of the garden and wreak havoc on wildlife habitat and agricultural lands.

One of these escapees is Ravenna grass (Saccharum ravennae), a large “ornamental” grass, also called “hardy pampas grass” or “plume grass.” It is so named for its resemblance to pampas grass, forming large 3 to 4 feet diameter clumps and producing 12 feet tall flowering stems topped by attractive silver feathery plumes. Unfortunately, the plumes produce plenty of minute seeds that are easily in spread wind and water.

Ravenna grass proliferates in gardens, irrigation drainage ditches, wetlands, and riparian areas where it can crowd out habitat, create impenetrable areas, and restrict stream flow. It could become a problem in eastern Washington along the Columbia and Yakima rivers and is already a serious problem in many other western states.

Where did it come from? Ravenna grass is native to the Mediterranean region and has been sold by the horticulture industry since about 1921 as a desirable ornamental grass. In fact, a quick search of the internet indicates that you can still buy it. Fine Gardening magazine touts its height as a striking vertical accent for the landscape and notes that it is deer, drought, and frost tolerant. Nevertheless, do not to buy it or plant it. It will spread via the seeds and become a weed problem in your yard, your neighbors’ yards, and beyond.

Our local Master Gardeners unsuspectingly planted some Ravenna grass several years ago in the Ornamental Grass garden of their Master Gardener Demonstration Garden. It thrived and spread itself throughout the entire garden and the neighboring library landscape. They were clued into this invasive grass by a local noxious weed board employee who advised seeking out all the plants in the garden and digging them out. (Ravenna grass is classified as a Class A noxious weed by the Noxious Weed Board of Washington, requiring all of us to remove it from our land.)

Before they could attack the Ravenna grass infestation, the Master Gardeners needed to know its identifying characteristics. Without the flowers or seed heads, it is often hard to tell one ornamental grass from another. However, Ravenna grass leaves are distinctive with a white mid-vein running the length of the 0.5 to 1 inch wide and 3 to 4 feet long blades. The blades are blue-green in color with very hairy bases.

Once they knew what it looked like, the Master Gardeners were ready to attack the grass by digging it out the plants and their roots because that is the most effective method of control in gardens and landscapes. There are not yet recommended chemical control recommendations for controlling Ravenna grass in home gardens.

The Master Gardeners found and removed over 200 smaller plants not yet producing flowers and seed along with the offending larger plants originally planted in the Ornamental Grass garden and responsible for the problem. They averted a noxious weed disaster in their garden, but this grass was unknowingly bought and sold to many other gardeners in our state before nurseries were made aware of the problem. If you have “hardy pampas grass” in your landscape, check it out, and get digging if you find that it is Ravenna grass. For more information on Ravenna grass consult the Noxious Weed Control Board of Washington at: http://www.nwcb.wa.gov/detail.asp?weed=193

Garden Tips, WSU Extension, Benton County, 5600-E West Canal Drive, Kennewick, WA 99336-1387, 509-735-3551, Contact Us

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